The present invention relates to a single or multi-step water extraction process for removing trimethyl phosphate (TMPO) from phosphorus containing pesticides having limited water solubility to produce a pesticide containing less than 1000 ppm TMPO.
A useful pesticide 2,2-dichlorovinyl dimethyl phosphate (DDVP), is disclosed in U.S. Pat. No. 2,956,073 wherein the DDVP is produced by reacting trimethyl phosphite (TMP) with chloral. The DDVP product often contains trimethyl phosphate (TMPO) which is an undesirable by-product. Other undesirable materials in the DDVP product include methanol, dimethyl methylphosphonate (DMMP), and dimethyl hydrogen phosphite (DMHP).
The present invention provides an economical and effective method for reducing the TMPO level below 1000 ppm for phosphorus containing pesticides by extraction with water. The pesticide may or may not be dissolved in a suitable solvent such as methylene chloride. In addition, the water extract removes other undesirable materials including methanol, DMMP, and DMHP.